Normally, duplex radios are expensive to build, are spectrally inefficient, and require duplexers. Methods other than full duplex presently being used for phone patch interconnects are lower cost, but are restrictive to conversation by requiring a push-to-talk (PTT) switch on one end and some type of talk permit indication on the other.
Quasi-duplex methods closely simulate full duplex operation, providing the user with a more natural and smoother-flowing conversation without the added cost of duplexers. Audio degradation may be present in the simplest quasi-duplex implementations; however, enhancement of performance, that can make a high tier system almost transparent to the user, is possible.